1. Field of the Invention
The present invention relates to motor vehicles and in particular to a restraint system for a hood lift device.
2. Description of Related Art
Devices for lifting the rear of a hood during an impact have been previously disclosed. Borg et al. (U.S. Patent Number 2006/0108169) is directed to a mechanical absorption system for an active bonnet hinge. Borg teaches a device that raises a bonnet during an initial collision using an actuator and a blocking device that is intended to block the actuator in a given position. Borg intends to provide a device that allows for impact absorption in the opposite direction of the direction that the bonnet is lifted, once a pedestrian has collided with the hood.
Borg teaches a safety device, including an actuator, a link rod, a raising lug and a locking hook. The safety device is associated with a bonnet. During an impact, a pyrotechnic charge exerts a thrust on the hook to release the link rod, causing a piston of the actuator to extend, which further raises the bonnet. As the actuator extends, a snap ring occupies a groove. At this point, the piston is prevented from extending any further. Borg teaches that this first phase corresponds to a phase of arming the safety device. During a second phase, force is applied to the piston by a pedestrian impacting the bonnet. This impact causes the piston to retract and the snap ring forcibly enters a small-diameter upstream part of a cylindrical body. This second phase corresponds to a phase of absorbing shock.
Kramarczyk et al. (U.S. Patent Number 2005/0264036) is directed to a hood elevation system. Kramarczyk teaches a hood elevation system for a motor vehicle, including an actuator configured to move a portion of a hood between an elevated and a retracted position. The hood elevating system also includes a self-locking mechanism. Kramarczyk teaches that the self-locking mechanism enables repeated elevation and retraction of the hood.
Kramarczyk teaches a hood that is attached to a vehicle by hinges adjacent to a windshield. Each hinge is operatively connected to a hood deployment linkage. Kramarczyk teaches that deployment of the linkage may be further associated with a motor via a self-locking mechanism. Kramarczyk teaches that the motor functions as an actuator to selectively move the hood between a retracted position and an elevated position by selectively retracting and extending a member. Kramarczyk also teaches that the motor is controlled by a sensing system.
The prior art requires systems with actuators including provisions to lock the piston, thereby increasing the complexity of the actuator. There is a need in the art for a system that constrains the lifting movement of the hood without the need to introduce additional components into the actuator system.